长脉冲激光辐照铝靶过程中熔池内液体的表面张力与熔池形状的关系
在假设铝靶熔化产生的熔池向外隆起形成鼓包和熔池内熔液发生喷溅形成熔坑并在固-液界面残留很薄一层液体两种情况下，数值求解了其表面张力的大小。分析得到了熔池内液体表面张力及其增量与时间的关系。
结果显示，铝靶受激光辐照产生熔池区域的大小与辐照时间成正比；在以上假设的两种情况下，激光作用铝靶时间越久，熔池内熔液的表面张力也越大；受激光作用前期,铝靶温度和熔液表面张力随时间变化率较大，辐照后期较小。
关键词 长脉冲激光 数值模拟 铝靶 表面张力 温度场分布
毕业设计说明书（毕业论文）外文摘要
Title The dependence of drag force induced by surface tension of and molten pool shape when long pulsed laser irradiates aluminum target
Abstract
Aluminum target’s temperature field distribution was obtained. A two-dimension axisymmetric model was established and the process of the raise of temperature in the aluminum target induced by laser irradiation is simulated by using the finite element method. The numerical solution of temperature in different time was obtained.
Numerical solution of the drag force induced by surface tension was obtained on the assumption that the molten pool shaped like hemisphere and only little melt attached on solid-liquid surface in the crater induced by ejection. The relationship between surface tension force and the molten pool shape was obtained.
The results show that the size of the molten pool induced by laser irradiation is proportional to the irradiation time.The longer the irradiation time is,the larger the drag force induced by surface tension will be in both cases supposed above.Additional,the raise rate of change over time of temperature and surface tension force at early stages is bigger than that of later period.
Keywords long pulsed laser,numerical simulation,aluminum target,surface tension force,temperature field distribution
目次
1 引言 1
1.1 激光技术概况 1
1.2 激光辐照材料的研究 1
1.2.1 国外研究状况 1
1.2.2 国内研究状况 2
1．3 本文的主要研究工作 3
2 理论基础 3
2．1材料受激光辐照的理论基础 3
2.1.1 激光与物质相互作用的过程 3
2.1.2 金属对于激光的吸收 4
2．2有限单元法原理 4
3 激光作用铝靶表面时的数值模拟 5
3．1温度场分析 5
3.1.1 传热学基本理论 5
3.1.2 二文轴对称模型下的温度场求解 6
3．2 数值模拟 8
3.2.1 有限元方程与数值求解 8
3.2.2 材料参数的非线性 10
3.2.3 熔池内液体表面张力的计算 11
4 数值结果与讨论 11
4.1熔液形成鼓包时的张力分析 13
4.1.1 径向方向上的温度场 13
4.1.2 轴向方向上的温度场 14
4.1.3 熔池固-液界面的演化 14
4.1.4 鼓包表面液体的张力 15
4.2 熔坑表面熔液的张力分析 16
4.2.1 径向方向上的温度场 16
4.2.2 轴向方向上的温度场 17
4.2.3 熔池形状演变 18